The idle air supplied to the engine at the idle time of the engine is separated into a normal idle air supplied in a normal temperature region including a hot time, and a first idle air supplied in a low temperature region of an engine atmosphere temperature.
In other words, in the normal temperature region of the engine, a predetermined idling operation of the engine is executed by the normal idle air.
Further, in the low temperature region of the engine, the first idle air increased in comparison with the normal idle air is supplied at a start time of the engine, and a low temperature start (a first idling operation) of the engine is executed by a hither rotational speed in comparison with the idling operation.
The supply of the normal idle air and the supply of the first idle air are particularly executed by an idle speed control apparatus shown in FIG. 2.
A description will be given with reference to the drawing. Reference numeral 20 denotes a single throttle body connected to a single cylinder engine via a suction air pipe (not shown). A suction air passage 21 is provided through in an inner portion of the throttle body, and the suction air passage is controlled so as to be opened and closed by a throttle valve 23 attached to a throttle valve shaft 22.
Reference numeral 24 denotes an air screw passage which bypasses the throttle valve 23, has a downstream side open to an inner side of a suction air passage 21a in a downstream side from the throttle valve 23, and has an upstream side open to a suction air passage 21b in an upstream side from the throttle valve 23. An air flowing within the air screw passage 24 is controlled by rotating an air screw 25 to variably adjust an opening area of the air screw passage 24.
In other words, the opening area of the air screw passage 24 can be reduced so as to reduce an amount of air flowing through the air screw passage 24, by the air screw 25 being adjusted to move in a downward direction in the drawing, and the opening area of the air screw passage 24 can be increased so as to increase an amount of air flowing through the air screw passage 24, by the air screw 25 being adjusted to move in an upward direction.
The air screw passage 24 mentioned above is used for controlling the normal idle air supplied to the engine in the normal temperature region including the hot time.
Reference numeral 26 denotes a starter passage which bypasses the throttle valve 23, has a downstream side open to the inner side of the suction air passage 21a in the downstream side from the throttle valve 23, and has an upstream side open to the suction air passage 21b in the upstream side from the throttle valve 23. The starter passage 26 is provided separately from the air screw passage.
A start opening and closing valve 28 operated so as to be moved by a drive member 27, in which a heat expansion and contraction material such as a wax or the like is sealed in an inner portion, variably adjusts an opening area of the starter passage 26, whereby an air flowing within the starter passage 26 is controlled.
In other words, in a low temperature state in which the engine atmosphere temperature is equal to or less than a fixed temperature, the heat expansion and contraction material reduces its volume, an operation lever 27a of the drive member 27 moves to a lower side in the drawing, and the start opening and closing valve 28 moves to a lower side in synchronous therewith so as to increase the opening area of the starter passage 26.
Accordingly, in addition to the normal idle air supplied from the air screw passage 24, the first idle air is supplied toward the suction air passage 21a in the downstream side from the throttle valve 23 from the starter passage 26, whereby it is possible to execute an engine start (a first idling operation) in the low temperature state.
On the other hand, in a high temperature state in which the engine atmosphere temperature is higher than the fixed temperature, the heat expansion and contraction material expands its volume, the operation lever 27a of the drive member 27 moves to an upper side in the drawing, and the start opening and closing valve 28 moves to an upper side in synchronous therewith so as to close the starter passage 26.
In accordance with the structure mentioned above, the first idle air is not supplied into the suction air passage 21a in the downstream side from the throttle valve 23 from the starter passage 26, but the normal idle air is supplied to the suction air passage 21a in the downstream side from the throttle valve 23 from the air screw passage 24, whereby the engine start in the higher temperature state than the fixed temperature is executed.
In other words, in the case that the engine atmosphere temperature is in the normal temperature region including the hot time, the engine start and the idle operation are executed by the normal idle air supplied from the air screw passage 24. On the other hand, in the low temperature region of the engine, the engine start and a thereafter warm-up operation are executed by the increased air obtained by adding the first idle air supplied from the starter passage 26 to the normal idle air supplied from the air screw passage 24.